Canadian archeology researchers have come up with a new theory to explain the perplexing abundance of Western European cave art that depicts disfigured human hands: people in some ancient societies ritually amputated their fingers to sacrifice them to a deity.

Previous studies of the artwork, which dates from the Upper Palaeolithic era some 22,000 to 27,000 years ago and can be found in France and Spain, have suggested that hundreds of images showing hands without their usual allotment of full-grown fingers were inspired by people who lost digits to frostbite or who had a propensity to bend them backward as a way of communicating.

But researchers at Simon Fraser University who considered a wealth of these images believe they probably portray the consequences of dark spiritual ceremonies, at which men, women and children would lop off parts of their fingers to curry favour with a higher power.

Writing in the Journal of Paleolithic Archaeology, Brea McCauley, David Maxwell and Mark Collard also conceive of this act as a bonding exercise, which would have left individuals in those early societies with a shared mark of their devotion to each other.

It’s just costly enough without being an infringement to your survival

“By cutting off a piece of your finger, everyone around you can see that you’ve done something to this severity that shows how committed you are to the god or to the group,” McCauley said in an interview. “It’s just costly enough without being an infringement to your survival.”

Ever since they attracted the notice of researchers in the 1950s, the images of severed hands at Grotte de Gargas, Cosquer Cave and other caves in various parts of France and Spain have spawned several competing hypotheses about their roots.

Ancient images of disfigured hands are shown at the Grotte de Gargas cave in southern France.Courtesy of Jean Clottes

Ian Gilligan, an Australian archeologist, recently told the U.K. magazine New Scientist that many of the hands display the effects of frostbite, given that they have intact thumbs and abbreviated middle, ring and pinky fingers. Researchers at England’s Durham University, convinced that Paleolithic societies were sophisticated enough to manufacture mittens, wrote in 2012 that it’s likelier the images are proof of a sign language in which humans interacted through hand gestures.

McCauley and her colleagues reached their conclusion by combing through an online ethnography database called the Human Relations Area Files to find cultures around the world that have engaged in systematic finger amputation. They identified 121 societies through history that undertook this gory practice for one of 10 reasons, including mourning a relative, punishing wrongdoers and staking out the group’s distinct identity.

Previously, if a skeleton was missing their finger bones, we wouldn’t really think too much of it

Sacrifice was the most common motivation in the sample — and, in the researchers’ view, the probable stimulus for the cave art. It’s believed the hands of several dozen people, including adults, adolescents and infants, were used to produce images at Grotte de Gargas, and McCauley said it’s conceivable they could have each hacked off a finger or three as part of a “negatively arousing” religious experience.

“You’re in a dark cave, where images are said to appear suddenly out of the darkness. Individuals have argued that people might be using mind-altering substances,” McCauley said. “We thought that within the context of this ritualized environment, sacrifice would make the most sense out of all of these different (reasons to amputate a finger).”

The researchers think other evidence discounts possibilities that don’t involve amputation. If the images pictured frostbitten hands, McCauley said, they’d likely be found across a vast area, wherever biting temperatures prevailed during the Palaeolithic age; instead, they are distributed erratically, within a handful of caves in different regions of France and Spain. And she doubts they represent an ancient sign language because they don’t include a pattern of bent thumbs, the easiest finger to contort.

Still, McCauley said, further investigation into the cave art is warranted. She’s hoping to advance her line of inquiry by studying how frequently fingers were amputated for medical reasons or menial accidents during this period, as well as by examining skeletal remains to see if their fingers were naturally misshapen.

“Previously, if a skeleton was missing their finger bones, we wouldn’t really think too much of it, because the archeological record is so patchy and small finger bones can deteriorate quite easily,” she said.

“But now, if we’re finding a lot of skeletons that are missing fingers, it might mean something different.”